1. Field
The following description relates to an optical structure for fingerprint acquisition, and more particularly, to an optical structure for acquiring a fingerprint with high-resolution and minimum distortion.
2. Description of the Related Art
Generally, user authentication by fingerprint recognition has been widely used due to the convenience of use, and superior security and economic efficiency. The conventional optical fingerprint acquisition device uses a prism to obtain a fingerprint. That is, in an optical fingerprint optical system including a total internal reflection prism, a resultant image captured by a lens may include keystone distortion due to the inherent optical properties of the optical system if the optical system employs no specific distortion correction technique.
Hence, various methods for acquiring an image with less distortion by correcting for the optical distortion have been introduced.
As the conventional distortion correction methods, an image sensor may be tilted, an optical unit for optical distortion correction may be added between a prism and an image sensor, or software may be used for distortion correction.
However, the method of tilting the image sensor cannot perform precise distortion correction, and the method of addition of the optical correction unit may cost too much, whereas the use of cheap optical element may result in degradation of optical performance (MTF, etc). Moreover, the use of software for distortion correction may take a substantial amount of time to produce an image having its distortion corrected due to the complexity of calculation.